Carburetor



Nov. 29, 1938-. R. E BRACKE v 2,138,592

' cARBUREToR Filed Feb. 20, 1935 3 Shets-Sheet l 2 J2 l@ l@ i! 642 26 Nov, Z9, y11938. R. F. BRAcKE CARBURET'OR Filed Feb. 20, 1935 3 Sheets-Sheet 2 R. F. BRACKE Nov. 29, 1938.

CARBURETOR 3 Sheets-Sheet 5 w 0 a j u 6 fw a 0 l m f8 /1 /w /M w w.

@j/7,2m@ im Pawnee ov. ce, 193s UNIT;

CARBURETUR Robert F. Bracke, chicago, m. Application February 20, 1935, Serial No. 7,3324y 8 Claims.

My invention pertains to carburetors and is particularly concerned with carburetors of the fuel lift type. The invention disclosed and claimed in this `application is an improvement 5 over that disclosed and claimed in my prior apl plication, Serial No. 6,421, filed February 14, 1935.

Under certain peculiar atmospheric conditions, dilculty was experienced with the carburetor'of my said prior application as a result of moisture condensing from the air and freezing on the secondary air valve, thereby temporarily rendering this air valve incapable of carrying out all of its normal functions in an eflicient manner. An object of my present invention is to provide a carburetor wherein the secondary air valve is so located relative to the vaporization of the fuel that this air valve is not subjected to the chilling eiect of such vaporization.

Another objectof my invention is to provide a carburetor having improved means for controlling the secondary air valve during choking of the engine.

v Another object of my invention is to provide a 25A carburetor having improved means for cracking the throttle during choking of the engine.

Another object of my invention is to provide a carburetor wherein the detrimental effects of backfiring are minimized.

Another object of my invention is to provide a carburetor having improved means for controlling the degree of suction obtaining in the fuel chamber.

Another object of my invention is to provide a carburetor having improved means for preventing fluttering of the secondary air valve. v

Another object of my invention-is to provide a carburetor having improved means for guiding the secondary air valve y`-to prevent cooking thereof.

Other objectsand advantages will become apparent as the description proceeds.

In the drawings,

Figure 7 is a diagrammaticshowing of a carburetor embodying my invention.

Referring to Figures 1 to 5, inclusive, ofthe drawings, I have illustrated my carburetor as comprising three main castings A, B and C, held together by bolts I8, there being suitable gaskets I2 and I4 clamped between the castings to provide an air-tight assembly.

Fuel enters the carburetor through an inlet I6 adapted to be connected to a main fuel tank by suitable piping. The fuel entering the inlet I6 passes into a filter chamber I8 in which there is provided any suitable ltering means, such, for example, as that disclosed in my said prior application. From the filter chamber I8 the fuel passes to a fuel chamber 20 containing a iioat 22 guided for Vertical movement on a cylinder 24. The oat 22 controls the usual inlet valve, not shown, through which fuel is admitted into the fuel chamber 20.

The primary air supply enters through a tube 26 whose upper end is adapted to be inserted into a suitable opening in any conventional type of air iilter and silencer of the kind now commonly used on automobiles. The air entering the tube 26 passes into a nozzle Venturi tube 28 havinga restricted throat terminating in a step just below which are the diagonal fuel feed passages 30. These passages 30 connect the throat of the nozzle 28 with an annular chamber 32 communi- 30 cating with a passage 34. 'Ihe passage 34 in turn communicates with the fuel chamber 20 by way of orice 36 and cylinder 24. The piston 38 of the accelerator pump is provided with suitable 28 into duct 40. 'I'he duct 40 has a cylindrical Figure lis a vertical section through a carburetor embodying my invention;

Figure 2 is a vertical section taken on the line 2--2 of Figure 1;

Figure 3 is a vertical section taken on the line 3-3 of Figure 1;

Figure 4 is a horizontal section taken on the line 4-4' of Figure 1; y

Figure 5 is a vertical section taken on the line 5-5 of Figure 2;

Figure 6 is a vertical section through the upper end of a modied'form of my invention; and

ports whereby fuel may be drawn from the fuel chamber to the throat of the nozzle 28.

The fuel entering the nozzle 28 through feed passages 30 mixes with the primary air and forms an incompletely vaporized mixture which isl discharged from the lower end of the nozzle 40 outlet 42 leading into the upper end of the mixing chamber 44' where the mixture of fuel and air delivered by the nozzle 28 mixes with secondary air.

This' secondary air enters the carburetor through horn 46 which has a reduced upper end adapted to be received in the same air filter and silencer which covers the entrance to the primary air tube 26. In the horn 26 is a throat member 50 48 held in place by a spring clip 5I). Throat member 48 has the internal shape of a large Venturi tube and is shown as being closed by a secondary air valve 52 which is held in the elevated position shown in Figure 1 by a spring 54 resting in the 55 base of a cup-shaped guide 56. Stops 53 limit the upward movement of the valve 52.

The guide 56 is urged downwardly against a transverse beam-like portion 58 of casting A by spring 60 whose upper end rests against the inturned ange of a sheet-metal stop 62. The lower end of stop 62- extends to a point just above the base of guide 56 and limits the upward movement of` guide 56 when a backfire occurs. The inturned upper end of the stop 62 rests against a spring clip 64 secured in a suitable groove in sleeve 66. f

The secondary air vlave 52 is drawn downwardly against the resistance of spring 54 under the influence of the suction obtaining in the mixing chamber 44. The interior `of air valve 52 is in constant communication with the upper end of mixing chamber 44 through tube 68, annular chamber 10, and restricted orice 12.

A pair of throttle' bores 14 and 16 communicate with the lower end of mixing chamber 44. Throttle bores 14 and 16 are provided with throttle valves 18 and 80, respectively, both of these valves being'mounted on a common shaft 82 connected with the usual accelerator pedal by means of an arm 84, and also connected with the usual hand throttle 4controlby means of a second arm 86.

When the throttel valves 18 and 80 are in the position corresponding to idling operation of the engine, these valves almost, but not quite, close the throttle bores 14 and 16.

Pistonl 38 of the acceleratorv pump is urged downwardly by spring 88 and is moved upwardly by piston rod 90 resting at its lower end on an adjustable plug 92 carried by arm 94 of a lever 96 having a second arm 98 connected by link |00 to branch |02 of lever 84 which oscillates with the throttle valve shaft 82. Piston 38 carries an economizer |04 having an4 enlarged and tapered upper end which restricts the flow of fuel through the knife-edged orifice 36 when the engine is idling and when it is operating under part throttle. When the engine is operating in full throttle, the reduced lower` end of Athe pin |04 is located in the orifice 36 and permits free flow of fuel to the nozzle 28. f

wardly away from the ends of ports |06 to per-` mit a greater iiow of fuel therethrough.

Piston 38 also includes relief means for preventing over-supply of fuel to the nozzle 28 when the throttleis suddenly opened over a wide range of throttle movement. This relief means comprises a second series of ports I|2 whose lower .ends are normally closed by a ring I|4 urged against them by a. light spring ||6. 'I'his spring l I6 yields when the throttle is suddenly opened over a wide range of throttle movement and permits back flow of fuel through the piston 38.

Part of the air entering the horn 46 passes downwardly outside of throat member 48 and into ducts ||8 and |20 communicating with a restricted orice |22 in choke plate |24. A sheet-metal cup |26 forms a chamber |28 on the side of choke plate |24 which is opposite ducts ||8 and |20` Air from chamber |28 can pass through a second opening |30 in choke plate 24 and thence through tubular member v|32 into booster Venturi tube.

-and restricts the-outlet for the 4booster |34 so 4into booster |34 but always maintains communie |34. Tubular member |32 carries a spring ring |33 which prevents 'the tubular member from dropping out when the choke plate |24 is removed. Booster |34 has a restricted throat terminating in a shallow step just beyond which are radial passages |36 which connect the throat of the booster with an annular space |38. The space |38 communicates through a passage |39 with the upper en d of the fuel chamber 20.

Booster |34 discharges into lduct |40. Air and any vapor which may be dischargedv into duct |40 passes through orifice |42 and lateral outlets |44 into the stream of secondary air which enters the carburetor around the secondary air valve 52.

It is important that the suction in the fuel chamber 20 be maintained constant under all normal conditions of engine operation, and for this purpose I provide a pin |46 having an enlarged head clamped between the air valve 52 and a plate |48 supported by spring 54. The lower end of the pin |46 is tapered and is located in orice |42 so that as the suction in the mixing chamber 44 increases, the air valve 52 is lowered. A largerportion of the pin 46 enters orifice |42 that a substantially constant degree of suction is maintained in the duct |40 located between the orifice 42 and the outlet of the booster. When the secondary air valve 52 is in lowered position, the lower end of pin |46 is received in a tube |50.

Between idling speed and an engine speed corresponding to approximately twenty miles per hour of vehicle travel, is a range requiring delicate control of the boosteroutlet. Itis therefore desirablel to have a relatively large kmovement of the restricting pin |46 during this range so that extreme accuracy of adjustment can be avoided. I therefore so design the throat memf ber 48 and secondary air valve 52 that a relatively large movement of this air valve occurs between these engine speeds, and this 'large movement of the air valve produces an equally great movement of the restricting pin |46 whose tapered lower end lies in the orifice |42 through which the booster discharges.

The desired idling setting of the carburetor is obtainedby controlling the degree of suction existing in the chamber |28. This chamber communicates with the engine side of throttle valves 18 and 80 by way of duct |52, port |54, bore |56, passage |58 and opening |30 in choke plate |24. A needle valve |60 controls this communication and this needle valve |60 constitutes the idling adjustment for the carburetor.

Figure 5 shows the position of the opening |30 when the choke plate |24 is in normal position. It will benoted that as the choke plate is shifted from normal to part choke position, the opening |30 restricts the flow of air from chamber |26 cation between chamber |28 and, suction passage 4 |58. When the choke plate 6| 24 is moved to the position of full choke, the opening |30 is moved entirely away from the inlet end of booster |34 and a very small orifice |62 is located opposite 0 the inlet end of the booster and forms the sole source of air supply for the booster.l The choke plate |24 is connected 'with the usualmanual choke control through ball-ended arm |64.

Choke plate |24 has a centrally located non- 7A fingers are urged against the air valve 52 to holdy it in closed position. When the choke plate |24 is moved to full choke position, a pin |16 engages and forms a rigid connection between iinger |12 and shaft |68 and positively holds the air valve 52 against opening. The pin |16 projects from a collar |11 which is secured to the shaft |68 by the same screw which secures one end offspring |14 to this shaft.

The upper end of duct |52 communicates with a transverse passage |18 (Figure 4) which is normally closed by shaft.|68. Shaft |68 has an opening |80 therethrough and lwhen the choke plate |24 is moved to part or full choke position, shaft |68 is turned so that opening |80 lies in part or full alignment with passage |18, depending upon the degree of application of the choke. This establishes communication between the space immediately below air valve 52 and the engine side of the `throttle valves 18 and 80 and has the same general effect as cracking the throttle Valves 18 and 80.

In the operation of my improved carburetor the primary air enters tube 26 from the air cleaner and silencer and passes into nozzle 28. A vacuum is created'in'the throat of the nozzle 28 and draws fuel from fuel chamber 20. This fuel fiows through diagonal feed passages 32 in the nozzle 28 and mixes with the primary air to form an incompletely vaporized mixture which passes into mixing chamber 44. The suction existing in mixing chamber 44 when the engine is operating normally draws the secondary air valve 52 downwardly and secondary air ows into the mixing chamber 44 around the air valve 52.

Further vaporization of therfuel takes place in the mixing chamber 44, and the vaporized mixture ows past the partly or full open throttle valves '18 and 80 to the engine. When the throttle valves are opened' through an appreciable range of movement, the piston 38 is raised' and injects an additional quantity of fuel into the nozzle 28, to permit rapid acceleration of the engine. If the throttle valves are opened suddenly through a wide range of their movement, the relief means in the piston 38 will act to prevent an over-supply of fuel to the nozzle 28.

When the engine' is idling or is operating at less than half of its full-speed, the secondary air entering through the throat member 48 landaround the air valve 52 creates an area of maximum suction which is located' a short distance below the largest diameter of the air valve. However, when the speed of the engine is increased to pin |46 correspondingly restricts the outlet for .the booster Venturi tube so that a. constant degree of suction is maintained on thel fuel chamber 20. This likewise contributes to the eiiiciency'of the nozzle 28 at high engine speeds. The consumption of excess fuel at idling and low speeds is prevented by the economizer pin 36.

When the choke is applied, the inlet to thel booster Venturi tube is restricted, and the degree of suction obtaining in the fuel chamber 20 is accordingly reduced. This results in a greater pressure drop between the fuel chamber and the throat of the nozzle 28 so that the nozzle 28 provides a richer mixture which facilitates starting and running of the engine When it is cold.

Application of the choke also opens a by-pass around the throttle valves which connects the space immediately below the air valve 52 with the .engine side ,of the throttle valves. At the same time this by-pass is created, the fingers and |12 are so moved as to resist to a greater 0r less degree the opening of secondary air valve 52. 'Ihis combination produces a high degree of suction in the space below the air valve 52 and produces an increased discharge of fuel and air by the nozzle 28. Some of this mixture flows to the engine past throttle valves 18 and 80 which are always slightly open, and the rest reaches the engine by way of the by-pass around these valves. The additional fuel supplied to the engine through the use of the by-passy tends to prevent stalling of the engine when it is cold.

My invention also contemplates means in the form of stop 62 to protect the carburetor against back-fire of the engine such as might occur during any period of engine operation. If the sheet metal stop 62 were not provided` to limit the upward movement of the guide 56, upward movement of this guide under the sudden force of a back-fire would either cause the upper end of this guide to engage the inner shoulder provided by the secondary air valvev 52, or would compress and be stopped by springs 54 and 60.l .If the upper end of the guide 56 were driven forcefully against the' inner shoulder of the secondary air valve, the upper end of the guide 56 would be distorted and forced outwardly against the secondary air valve with the resultv that this air valve would stick and fail to Doperate properly. .On the other hand, if the force of the explosion were exerted upon the springs 5,4 and 60, these springs might be distorted to such an extent that injury would result and again the smooth operation of the secondary air valve would be impaired.

In Figure 6 I have shown, im cross-section, the upper end of a modiied form of my invention. In this form the'horn |84 supports a dash-pot cylinder |86 containing a piston |88 mounted on the uppenend of piston rod |90 which reciprocates with secondary air valve |92.

The piston |88 and cylinder |86 constitute an air dashpot for preventing iiuttering of the secondary air valve |92. The tendency of this air 'valve .to utter is particularly great when the air valve is only slightly open and the dashpot which I have provided is particularly effective under these conditions. When the air Valve |92 has moved an appreciable distance from closed position, the piston |88 uncovers the upper end of a passage |94 which permits a limited amount of air to enter the upper end of cylinder |86 and reduces the dashpot action of the cylinder and the further advantage ofvproviding improvedv guiding means for the.air valve |92 to prevent. cooking of this air valve. 'Ihe lower portion |96 of the piston rod |90 is guided in the sleeve |98 which corresponds to the sleeve 66 of the embodiment shown in Figure 2, whereas the upper vvend of the piston rod is guided by the piston Hi8` so that there is a guide for this piston rod on each side of the valve |92. It is to be understood that the extreme lower end of the piston rod |96 has the same tapered conformation as the lower end of pin |46' in Figure 2 and performs the same function that this pin performs. Except for the distinctions which I have mentioned, it is to be understood that the modification shown in Figure 6 is identical with that shown in the rst i'lve figures of the drawings.

It is to be understood that my invention is not limited to the specic structure shown in the drawings but that my invention may assume various forms andthat the scope of my invention is to be limited solely by the following claims.

I claim:

.1. In a carburetor of the class described, the

combination of a nozzle, a primary air inlet for supplying air to said nozzle, a fuel chamber from which said nozzle is supplied, a booster for creating suction in said fuel chamber, a valve for admitting secondary air, a pin operated by said valve and controlling the degree of suction created by said booster in said fuel chamber, a tube for receiving the end of said pin, said tube being located some distance from said valve, a discharge conduit 'for said nozzle surrounding said tube, said discharge conduit terminating in a mixing chamber wherein the mixture delivered' by said nozzle mixes with secondary air admitted past said valve, said mixing chamber being of reduced cross-section adjacent the discharge end of said conduit, and valve means for connecting said mixing chamber with a source of suction.

2. In a carburetor of the class described, the combination of a nozzle, asource of fuel supply therefor, a primary air inlet for said nozzle, a secondary air valve, a spring for closing said valve, said valve being opened by a pressure differential created on the opposite sides thereof, a mixing chamber into which said nozzle and secondary air valve discharge, a throttle bore communicating with said mixing chamber, a valve in said bo-re, a by-pass passage around said last named valve, a finger for resisting opening of said air valve, a shaft for moving said finger into and out of engagement with saidair valve, said shaft intersecting said by-pass passage, and a port in said shaft controlling said by-pass passage. I

3. In a carburetor of -the class described, the

combination of a nozzle, a source of fuel supply therefor, a mixing chamber into which said dnozzle discharges, a primary air inlet for said nozzle, a secondary air valve for admitting additional air to said mixing chamber, said air valve being spaced from said mixing chamber, a

throttle bore communicating with said mixing chamber, a throttle valve in said bore, a by-pass connecting the engine side of said throttle bore with the space between said mixing chamber and said secondary air valve, choke means for enriching the mixture supplied by said nozzle, and a valve in said by-pass controlled by said choke means. y 4. In a carburetor of the class described, th combination of a nozzle, a source of fuel supply therefor, a primary air inlet for said nozzle, a secondary air valve, a movable cup-shaped guide for said air valve, resilient means for holding said guide in normal position, and other means for limiting movement of said guide away from normal position in the event of a backre.

5. In a carburetor of the class described, the combination of a nozzle, a source of fuel supply therefor, a primary air inlet for said nozzle, a"

secondary air valve, a movable cup-shaped guide for said valve, a cup-shaped stop located in said guide, a support for said stop, and a spring conned between the bottom of said cup-shaped guide and the bottom of said cup-shaped stop, said spring maintaining said guide in normal position.

6. In a carburetor of the class described, the

` combination of an air valve having a seat of'Venturi tube form, a mixing chamber to which air is supplied past said air valve, said mixing chamber having a part formed like a Venturi tube, a nozzle discharging into said mixing chamber at a point adjacent that part of the mixing chamber formed as a Venturi tube, a iioat chamber from which said nozzle is supplied with fuel, a

booster Venturi tube for creating a suction in said float chamber, said booster Venturi tube discharging into said mixing chamber, and means operated by said air valve for controlling communication between said booster Venturi tube mixing chamber communicating with said inletand having a portion formed as a large Venturi tube, a nozzle discharging into said portion of the mixing chamber, a fuel chamber constituting a source of fuel supply for said nozzle, a booster for creating a suction in said fuel chamber, said booster discharging into said mixing chamber intermediate said Venturi tubes, and means operated by said inlet valve for controlling communication between said booster and said mixing chamber.

8. In a down draft carburetor of the class described, the combination of a mixing chamber, a nozzle Venturi tube discharging into said mixing chamber, said nozzle Venturi tube constituting a primary air inlet for said mixing chamber, a source of fuel supply for said nozzley Venturi tube, an air valve for admitting secondary air to said mixing chamber, a throttle bore for connecting said mixing chamber witha source of suction, a throttle valve in said throttle bore, said air valve being separate from said nozzle Venturi tube and being mounted for movement Y responsive to variations in the degree of suc- `cylinder is filled with air, a piston rod, a oonnection between said piston rod and said yair valve, and means comprising asingle restricted atmospheric vent'communicating with said cylinder adjacent one end thereof for decreasingV the effectiveness of said dashpot when high degrees o-f suction obtain in said mixing chamber.

ROBERT F. BRACKE. 

